To me, this says that it's the composition that disturbs you.

Many people have pointed out that Klimt was threatened by women which is why their hands always look like claws. He also clumps his humans in with abstract color, but it's "human" "abstract color". He follows the rule of thirds, his compositions are balanced.

Mucha used color and ornament to great effect (combined with photorealistic faces) and your response is "commercial." Which, yes, they were. Although I'd be curious as to how you regard the Slav Epic:

Regardless, it's clearly not Chagall's use of color that disturbs you.

Your reaction to Giacometti cements my thinking. Giacometti is all about framing in that he eliminates all but the human form, warped. You can't help but regard his art as a play on framing as you must regard it in relation to yourself.

Chagall frames in a deliberately random-looking way. You find it disquieting because he's aware of the rules and distorting them for effect. You find that effect displeasing because framing is an important part of your artistic style... in the direction opposite Chagall.